Radioimmunologic Measurement of Human Placental Lactogen in Plasma by a Double Antibody Method During Normal and Diabetic Pregnancies

Abstract

A double antibody radioimmunoassay for human placental lactogen (HPL) in human plasma is reported. HPL was detected in maternal plasma by the 8th week of gestation, and there was a progressive increase in mean plasma HPL concentrations throughout pregnancy. Maternal plasma HPL concentrations at term were 1000 times greater than normal growth hormone levels, but HPL content of cord plasma was barely measurable. Four hr. after delivery of the placenta, plasma HPL was virtually undetectable. The half-life of endogenously secreted HPL in the plasma was shown to be 21[long dash]23 min, which suggests that the placenta must synthesize 3[long dash]12 g of HPL/day in order to maintain the plasma HPL concentrations observed during the last month of gestation. During comparable periods of pregnancy, the levels of circulating HPL in the normal and the diabetic subjects were not significantly different.